Optical component suitable for use in glazing

ABSTRACT

An optical component comprises at least one substantially planar element having a plurality of elementary surfaces capable of acting to reflect by total internal reflection light incident thereon through the corresponding said element within a first range of incident angles associated with each surface, and to refract light incident thereon through the corresponding said element within a second range of incident angles associated with each surface. Refracted light at low angles of incidence passes straight through to provide a view through the component.

BACKGROUND OF THE INVENTION

The present invention relates generally to an optical component suitablefor use in glazing, and in particular in glazing openings in fixedstructures such as commercial, industrial or domestic buildings. Thepresent invention will hereinafter be described with specific referenceto its application to such fixed structures without prejudice to thegenerality of the invention, however, which may nevertheless be used inother applications where its characteristic optical features may befound to be of utility. In particular, this may include, withoutlimitation, glazing for openings in vehicles, or for covering the exitopening of light sources or light transmission devices.

It is known that the intensity of illumination provided by daylightincreases generally with higher angles of elevation of incident light.This may be influenced on clear days by direct sunlight, in which casethe peak intensity may lie at a lower angle in dependence on theelevation of the sun. For this reason the illumination within a buildingby daylight entering through window or other openings is recognised tohave greatest intensity closest to and immediately beneath the windowopening, and to reduce in intensity with an increase in distance fromthe window. For the purposes of the present specification the term"window" will be understood to refer to any opening in a vertical ornear-vertical (that is upright) wall or facade, whilst an opening in ahorizontal or inclined surface will be termed a roof light.

For most commercial buildings where the occupants are expected to beworking on horizontal surfaces such as desks or tables, it has becomeconventional for the majority, if not all of the external surfaces to beformed as glazed window openings apart from any essential structuralcomponents required to support the glazing. Buildings having a depthgreater than that which can be illuminated even from totally glazedoutside walls require permanent artificial lighting. This, however,constitutes a considerable consumption of energy, and it has beenestablished that the energy consumption within large office blocks forillumination is in general greater than the energy consumption forheating in winter and/or cooling in summer.

The problem of glare is also encountered in such buildings, and this isgenerally approached by use of physical barriers such as blinds, whilstexcess thermal input is approached by the use of optical coatings and/orair conditioning both of which can be adjusted to suit the immediateenvironmental conditions.

The present invention seeks to address the above problems by providingan optical component suitable for use as part of, or in associationwith, a glazing panel across an opening in a structure which will act todirect incident light into the building in such a way that it is moreuniformly distributed through the interior.

Known so-called "daylighting" systems for improving the interiorillumination through glazed windows act to divert incident light at highelevations by reflection at silvered surfaces so that the light isdirected into the interior of the building at a higher angle ofelevation than it would if transmitted through a conventional windowpane where, by falling on a horizontal surface close to the window(which typically would not have a high degree of reflectivity), it isabsorbed and therefore not available for use. One known such system alsoincludes pivoted reflectors capable of being orientated such as todivert direct sunlight away from the building in order to reduce glare.Known such systems have the significant disadvantage that the reflectingsurfaces act as a barrier to direct viewing through the windows and,therefore, although the distribution of daylight within the interior isimproved the improvement is obtained only at the expense of a loss orreduction in visibility through the windows.

The present invention seeks to provide an optical component which, whenused to enhance the illumination by daylight within a building interior,nevertheless allows those inside the building to obtain an almostnormal, undistorted view through the window.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, an optical componentcomprises two substantially planar elements each having a respectiveplurality of elementary surfaces capable of acting to reflect by totalinternal reflection light incident thereon through the correspondingsaid element within a first range of incident angles associated witheach surface, and to refract light incident thereon through thecorresponding said element within a second range of incident anglesassociated with each surface.

Elementary surfaces on each element may have the same form, a similarform, or may be different from one another.

In one embodiment of the invention the at least one optical element hasa generally planar form with two opposite major faces and a plurality ofregular surface formations on the face, opposite the said one face, fromwhich light exits in use, the said surface formations acting to divertlight passing through the component by refraction and reflection intothe said two different directions.

The said elementary surfaces may include reflector interfaces at whichreflection occurs. The elementary surfaces may be regular and uniform ormay be non-uniform such that, for a given angle of incidence, the angleof reflection is different at different points of incidence over thesurface of the component. This may assist in avoiding glare as will bedescribed in more detail below.

For example, if for a given angle of incidence, the angle of reflectionis greater at points of incidence closer to a lower edge of thecomponent in relation to a normal upright orientation of use, than atpoints of incidence further from the said lower edge, this serves notonly to spread the reflected light over a wider angle, thereforeminimising the potential for an observer to be dazzled by aconcentration of light in one direction (namely, that arriving from thesolar disc) but also has other benefits in avoiding "hot spots" ofillumination as will be discussed below.

The reflector interfaces may be planar, and set at differentinclinations (either progressively or irregularly) to achieve therequired spread, or may be curved either convexly or concavely.

In a preferred embodiment of the invention suitable for use in glazingapplications the elementary surfaces are formed as asperities whichinterpenetrate one another; that is, the asperities of one elementinterpenetrate the corresponding asperities of the other element.

At least some of the elementary surfaces of the two said elements maytouch one another, either by direct contact or via an adhesive orinterstitial medium such as water or a gel. The medium may have the samerefractive index as the material of the elements, or a differentrefractive index, and the choice of these values will affect the opticalbehaviour of the component.

In a preferred embodiment of the invention each element has two sets ofelementary surfaces formed as elongate planar faces inclined to oneanother to define parallel V-section grooves in a major face of theelement. The grooves may be separated from one another or may becontiguous.

In other embodiments the grooves may be defined by a number of surfaceelements greater than two. For example two or more surface elements maydefine one side of a groove. Of course, the surface elements are notnecessarily planar, and curvilinear surface elements may also beutilised. The curvature of such elements may be simple curvature in oneplane (which may be orthogonal to or parallel to the major face of theplanar element, or may be a compound curve both parallel to andorthogonal to the said major face.

By appropriately selecting the aspect ratio (that is the ratio betweenthe depth and width) of the grooves, together with an appropriate choiceof separation between adjacent grooves, it can be arranged that thevisibility through an optical component formed as an embodiment of theinvention is substantially unobstructed over the range of anglessubtended at the eye of an observer for which the field of view ofinterest lies. In other words, it is appreciated that the field of viewof interest through a window for a seated or standing observer lies oneither side of a horizontal plane such as to subtend an angle at the eyeof the observer approximately in the region of ±15°. Above 15° themajority of the image is sky which, for the most part, is not observedin detail by the occupants of a room.

In order that the view through the component shall be undistorted it isimportant that the two major faces each have at least a proportion oftheir respective surface area substantially parallel to one another: insuch an embodiment the elementary surfaces acting to divert incidentlight into two separate directions thus occupy a proportion (andpreferably a minor proportion) of the overall surface area of thecomponent.

The elementary surfaces may be symmetrical or asymmetrical in crosssection and the arrangement may be such that at least over certainangles of incidence, light is reflected by the component rather thanbeing transmitted therethrough, although at other angles of incidencelight may be both reflected and transmitted.

Specific embodiments of the invention may be formed with cooperatinginterfaces acting to provide a plane reflector effect.

Between cooperating elementary surfaces there may be void spaces whichmay contain any selected fluid such as air, gas, or a liquid of selectedrefractive index, and the component may have means by which the contentsof the void spaces may be changed whereby to change the effectiveoptical performance by varying the refractive index of the material inthe void spaces.

Embodiments of the present invention may be made by micro-replicationtechniques utilising plastics film material which may be self-supportingor may require support on a transparent substrate such as glass, whereasother embodiments of the invention may be formed directly from aself-supporting material such as glass.

In either case the elementary surfaces may be formed as the faces ofgrooves in a major face of the element, and the grooves may be formed bythe use of a forming tool or other former, and in certain cases whichwill be described hereinbelow, the formers may be left in place sincethe total internal reflection at the interfaces defined by the formerseffectively ensures that these are "invisible".

The grooves of cooperating elements, which grooves define the elementarysurfaces referred to above, may be in register with one another acrossthe interface between the two elements, or may be out of register by apredetermined phase, and may be symmetrical or asymmetrical according tothe function the optical component is required to perform.

Another embodiment of the invention is formed to be able to act also asa sun blind, in which there are further provided means for diverting aproportion of light incident on the said one face in such a way that ittravels away from the component on the same side thereof as the said oneface.

The elements comprising an optical component formed as an embodiment ofthe present invention may be monolithic elements and the component maybe supported on at least one face thereof by a substantially rigidplanar transparent panel. The optical component may alternatively besupported on two opposite faces by respective substantially rigid planartransparent panels.

In an optical component formed as an embodiment of the present inventionthe surface formations may give rise to one or a plurality of chamberswithin the component, which may be infused by different fluids to changethe optical characteristics of the panel. This may allow the panel to beadapted to take account of changing environmental conditions, and inparticular to switch in a sun blind effect by appropriately varying therefractive index of the material within the chambers. This will bedescribed in more detail hereinbelow with reference to the specificembodiments.

The composite glazing panel may be adapted to be fitted as an auxiliaryelement to an existing glazing structure of a building, or may beadapted to constitute a glazing element of a permanent glazing structureof a building. The panel may, when fitted, be fixed in its orientation,or may be incorporated in a support structure enabling the orientationand/or position of the panel to be varied selectively.

According to a further aspect of the present invention, an opticalcomponent comprises at least one planar element having a plurality ofelementary surfaces inclined to a major face thereof, in which thedimensions of and separation between the elementary surface elements arenot substantially larger than about the pupil of the human eye (1 mm)and not smaller than that at which diffraction effects predominate(about several micrometers).

Various embodiments of the present invention will now be moreparticularly described, by way of example, with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating the variation in intensity oflight incident in a room through a conventional window;

FIG. 2 is a diagram illustrating the distribution of illumination withina room fitted with a glazing component formed as an embodiment of thepresent invention;

FIG. 3 is a view, on an enlarged scale (but not to scale) of an opticalcomponent formed as a first embodiment of the present invention, inposition in a glazing panel;

FIG. 4 is a schematic view illustrating an optical component having adifferent aspect ratio in a composite panel;

FIG. 5 is a schematic view, similar to that of FIG. 6, illustrating afurther embodiment having two optical elements;

FIG. 6 is a schematic view illustrating an embodiment such as that shownin FIG. 5, in which the two elements are in contact with one another;

FIG. 7 is a schematic view of a further alternative embodiment in whichthe two elements have surface features which are offset from oneanother;

FIG. 8 is a schematic diagram illustrating an embodiment of theinvention in which the surface features have a different form from thatillustrated in the preceding embodiments;

FIGS. 9 and 9a are ray diagrams illustrating the path of light raysthrough an embodiment designed to give a sunblind effect;

FIG. 10 is a schematic view of another embodiment of the inventionutilising partly silvered reflectors;

FIG. 11 is an expanded view, not to scale, of the embodiment of FIG. 10for the purposes of explanation;

FIG. 12, 13 and 14 are enlarged diagrammatic views of elements suitablefor use in further embodiments of the invention;

FIG. 15 is a schematic sectional side view of a first embodiment of thepresent invention;

FIG. 16 is a similar sectional view through a second embodiment of theinvention;

FIG. 17 is a sectional view through a further embodiment of the presentinvention having symmetrical elementary surfaces;

FIG. 18 is a sectional side view, of a further embodiment of theinvention having asymmetrical elementary surfaces;

FIG. 19 is a sectional side view similar to that of FIG. 18, in whichthe asymmetric elementary surfaces are oppositely inclined;

FIG. 20 is a sectional side view, on an enlarged scale, of an embodimentof the invention having particularly valuable characteristics;

FIG. 21 is a sectional side view of another embodiment havingsymmetrical elementary surfaces, but in which the aspect ratio isdifferent leading to different optical properties;

FIG. 22 is a sectional side view of an embodiment of the inventionhaving a regular array of three elementary surfaces;

FIG. 23 is a sectional side view of an alternative embodiment formedusing different materials and manufacturing techniques;

FIG. 24 is a sectional side view of a further embodiment made usingtechniques similar to those of the embodiment of FIG. 23;

FIG. 25 is a sectional side view of a further embodiment havingasymmetric elementary surfaces made using the techniques used for theembodiments of FIGS. 23 and 24; and

FIG. 26 is a sectional side view of an embodiment made using a pluralityof formers.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings FIG. 1 illustrates the distribution oflight within a room generally indicated by the box 11 passing through awindow generally indicated 12 by daylight generally indicated 13 passingtherethrough. For the purpose of illustration daylight passing throughonly a single point in the window has been illustrated, and forillustrative purposes the light has been represented by bundles of rayswith the number of rays in each bundle being representative of theintensity of daylight from that range of directions. Thus, it will beseen that at a relatively low angle of elevation the bundle indicated13a has only three rays, indicating a low intensity, whilstprogressively at higher elevations the bundles indicated for example13f, 13g and 13h have many more rays. The intensity of illumination fromthe notional bundles of light rays 13a-13h has been illustrated by theletters a-h along the floor and internal wall of the room 11, where theintensity of illumination is represented by the closeness of spacing ofthe incident rays. For comparison purposes it has been supposed that atable 14 is placed within the room 11 at a fixed position spaced fromthe window 12 and, for a given level of average illumination the lightfalling on the horizontal surface will be considered to represent abasis illumination of 100%.

FIG. 2 shows the distribution of light in a building through a windowopening equipped with an optical component of the invention. The samereference numerals to identify light beams as used in FIG. 1 have beenallocated, but it will now be seen that the total amount of lightarriving at the surface of the table 14 is almost twice as much asarrived for the same external illumination through a traditional windowas illustrated in FIG. 1. Moreover the distribution of light arriving atthe horizontal or floor surface closer to the window is more uniform.If, instead of a plain reflector on the ceiling, a reflector havingfacetted reflecting surfaces is used, the light may be directed from theceiling in any chosen direction. In FIG. 2 it will be appreciated thatthe minor proportion of beam 13a reflected is too small to show on thisscale and consequently the incident area a on the back wall issubstantially the same as in FIG. 1, whilst the incident beam 13h issubstantially entirely reflected so that no corresponding area h on thefloor close to the window is seen. The ceiling areas have beenidentified with the same reference letters to indicate light arrivingfrom the incident bundles identified by the same reference letters onthe floor and wall areas.

It is assumed in the discussion in relation to FIGS. 1 and 2 that thewindow 12 comprises a plane sheet of transparent material such as glass,or two such sheets in a conventional double glazing configuration. InFIG. 3 there is shown a part of an optical component forming anembodiment of the present invention located in the cavity between twoglass panels or a conventional double glazing cell identified as anouter glass panel 15, an inner glass panel 16 spaced by an air gap 17.The relative thicknesses of the glass and of the air gap are not toscale in relation to the optical component, generally indicated 18located in the air gap 17.

The optical component 18 comprises a transparent body having asubstantially flat planar face 19 and an opposite face 20 in which areformed a plurality of horizontal v-shape grooves 21. Each groove 21 isdefined by two flat surfaces, namely a first, or reflecting surface 22which is orthogonal to the planes defined by the major faces 19, 20 ofthe component 18 and a second surface 23 which is inclined at a shallowangle to the first surface 22.

As will be described in more detail below, light incident on the outerpane 15 of the double glazing cell is transmitted to the major face 19of the optical component 18, which will hereinafter be referred to asthe incident face, and travels through the body of the optical component18 until arriving at either the first surface 22 of one of the grooves21, or the major face 20 of the optical component 18 itself, which willhereinafter be referred to as the exit face of the component. Becausethe first surface 22 of each groove 21 is perpendicular to the majorfaces 19, 20 all light incident of the component 18 at angles above thehorizontal will travel through the body 18 to reach either the exit face20 or a first surface 22 of a groove 21. Light above the horizontal isof primary interest as it constitutes the vast majority of the lightarriving at a building. Light arriving at an angle below a horizontalelevation is reflected from the ground or surrounding objects, is verymuch less intense, and for practical purposes of illumination can beneglected as being of insignificant intensity to affect theillumination. It will be appreciated that the dimensions and proportionsof this optical component have been shown out of scale for the sake ofclarity of explanation.

FIG. 4 illustrates an embodiment in a more practical form in whichaspect ratio w/d is very much smaller. In this embodiment the opticalcomponent, now identified with the reference numeral 25 again has aplurality of grooves 26, each groove having a first surface 27 which isperpendicular to the major faces 29 and 30, but as will be seen fromFIG. 4 the width w of each groove is reduced to a very low value incomparison with the embodiments of FIGS. 2 and 3, and likewise the depthd of the grooves 26 is a smaller proportion of the overall thickness ofthe optical component 25 than in the embodiments of FIGS. 2 and 3. As inthe embodiment of FIG. 2 the optical component 25 has its incident face29 in contact with an outer pane 15 of a double glazing cell and itsexit face 30 spaced from an inner pane 16 by an air gap 31 which may bethe same as or different from the size of the air gap 17 in theembodiments of FIGS. 2 and 3. In practice the width of the grooves maybe made significantly less than the pupil of the eye so that the groovesare virtually invisible.

It will be appreciated that the proportion of light reflected at anygiven angle can be varied by changing the aspect ratio of the grooves.In addition, it is possible to vary the inclination of the two surfaces22, 23 defining each groove. Again, this allows the designer to vary theratio between transmitted and reflected light at any angle so thatreflected light entering the room in an upward inclination may then bereflected from a highly reflective sealing to arrive at a horizontalsurface such as a table or working surface, set deeper into the roomthan it would otherwise reach through a plain conventional window. Inthis way light arriving at the window can be distributed having beensplit into two components, in such a way that an interior volume withina building can be more uniformly illuminated by windows in a facade.

FIG. 5 illustrates a further embodiment of the invention, in which thereare two optical components 41, 42 facing one another. The opticalcomponents 41, 42 are made to the same form as the component 18 in FIG.2, with the exception that component 42 is reversed such that incidentlight arrives first at the major face having the plurality of grooves.Depending on the nature of the material from which the components 41, 42are made the planar outer surfaces 43, 44 may constitute the externalsurfaces of the glazing panel, or each component may be supportedagainst a glass pane as in the earlier embodiments. As can be seen inFIG. 7 the two optical components 41, 42 are positioned such that theirgrooved faces 44, 45 are spaced from one another although, as can beseen in FIG. 8, the two components may, in an alternative embodiment, bein contact with one another.

FIG. 6 illustrates three different sets of rays passing through theoptical component. Here, incident light at the shallow angle, indicatedLs, is diverted by reflection and refraction into three beams, a first,transmitted beam Lst, a second, reflected beam Lsr, which is reflectedfrom the horizontal "first" surfaces of the grooves, and a secondreflected beam which is reflected from the lower "second" surfaces ofthe grooves in the outer component 41, and then subject to a secondreflection, this time at a higher angle of incidence, at the "first"surface of the inner optical component 42 to produce a highly divertedbeam Ls2r. At intermediate angles of incidence shown by the incidentbeam Lm the majority of light is reflected into the reflected beam Lmrwith only a minor proportion passing through the component to form thetransmitted beam Lmt. At higher angles of incidence, such as thatillustrated by the beam Lh (which may be, for example, in the region of70° elevation from the horizontal) all of the incident light isreflected at the "first" surfaces of the grooves with none beingtransmitted although, due to interception at the lower or "second"surface of the inner optical component 42 a proportion of the reflectedlight is reflected a second time to form a second reflected beam Lh2r.

In an embodiment such as that illustrated in FIG. 6 the closed voidsdefined by the facing grooves on the inner faces of the opticalcomponents 41, 42 can selectively be filled with a liquid having thesame or substantially the same refractive index as the material in theoptical components 41, 42, in which case all of the incident light willbe transmitted substantially undeviated so that the day light may bedirected towards the ceiling or towards the floor selectively. Thisallows a "sunblind" effect to be achieved in circumstances where theoptical component is designed to divert a major portion of the incidentlight towards the ceiling thereby avoiding glair from direct sunlight.In low incident light conditions the fluid can be introduced into thevoids to allow the light to enter directly.

Turning now to FIG. 7, an alternative embodiment utilising two opticalcomponents 41, 42 is shown in which the grooves in the components areoffset from one another by half the pitch between adjacent grooves. Asillustrated in FIG. 9, at an elevation of 45° all of the incident lightis reflected. Notwithstanding this, at lower angles of incidence a majorproportion of the light is transmitted to allow direct viewing throughthe component.

FIG. 8 illustrates another "sun blind" configuration in which twooptical components 41, 42 are again used. The grooves in the twocomponents 41, 42 are positioned facing one another and in register, butthe spacing between the components 41 and 42 is chosen such that, at acertain angle of elevation, say 45°, (and above) all of the incidentlight is reflected towards the ceiling and none is transmitted. Belowthis angle of incidence a small proportion of the light is transmittedand at horizontal (that is 0° elevation) incidence substantially all ofthe light is transmitted.

FIG. 9 illustrates an alternative embodiment of the invention in whichthe spacing between the grooves is zero. In FIG. 11 only an opticalcomponent 50 is illustrated although, as before, it may be supported oneither its incident face 51 or its exit face generally indicated 52 by apane of glass, or by a pane of glass on each face. The grooves formed inthe exit face 52 are identified with the reference numeral 53 and eachcomprise, as before, two planar faces 54 and 55 with the aspect ratio ofdepth to width d:w chosen as 0.73. The two surfaces 54, 55 effectivelydefine reflector and refractor facets and, as can be seen by the raytrace in FIG. 11a, at an incident elevation of 45° a proportion of thelight is reflected upwardly towards the ceiling whilst a correspondingproportion is reflected upwardly and away from the building. It will beseen from the inset drawing FIG. 11a illustrating one ray path that thelight reflected away from the building is in fact reflected three times,twice by total internal reflection at the facet 55 and once byreflection at the facet 54 which may be silvered for this purpose inorder to achieve reflection at a high angle of incidence. Such anembodiment is useful where it is desired to restrict the amount of solarenergy entering a building. In such an embodiment, of course, directobservation through the window is not available except for a narrowrange of angles of incidence below 0°.

If both a sun blind effect and vision through the window at horizontalor near horizontal angles are required this can be achieved with anembodiment such as that illustrated in FIG. 10. In this embodiment agrooved optical component 50 such as that illustrated in FIG. 9 isbacked by a correspondingly shaped grooved optical component 60 with itsgrooves intercalated with the crests separating grooves in the component50. This has been shown on an enlarged scale in order to illustrate theinter-relationship between the two components. The relative positioningof these two components allows light at shallow angles to pass throughwithout substantial aberration.

FIG. 11 illustrates an embodiment such as that of FIG. 10 showing theray trace for light at 45° elevation which is partly reflected into thebuilding with a major proportion being reflected away from the building.Although represented as a single line the interface between the twocomponents necessarily involves a small gap to achieve the totalinternal reflection. In this respect the gap shown in FIG. 10 the scaleof which is enlarged laterally to emphasise the provision of the gap maybe extremely small providing it is sufficiently large to allow thephenomenon of total internal reflection to occur.

The embodiments of FIGS. 12, 13 and 14 address the problem of reflectionof the solar disc upwardly by the reflector facets of the opticalcomponent of the invention. Although it is true to say that the lightincident on a glazing panel arrives from a wide range of directions,there is the possibility that on cloudless days, when the sun is in acertain range of positions, a concentration of light arrives directlyfrom the solar disc. This has two disadvantageous effects: the first ofthese is the above-mentioned risk of glare or dazzling by upwardlyreflected light being viewed by an observer looking downwardly at thelower part of a glazing panel, for example from a standing positionclose to the glazing panel within a room. Although this would notnecessarily be worse than the glare arriving directly from the sunthrough a conventional glazing panel, its unexpected orientation maycause difficulties, especially since in this situation the observer maywish to view through the glazing panel to see the surroundingenvironment. The embodiment of FIG. 12 addresses this problem byproviding grooves 17 which, instead of having constant inclination, havean inclination of at least one face (namely the reflector face) whichvaries from top to bottom of the panel. In FIG. 12 the embodiment hasbeen illustrated on an enlarged scale to show four grooves the relativeinclinations of which have been exaggerated for the sake of clarity.These grooves are identified 70, 71, 72 and 73, each being defined by anupper or reflector facet 70a, 71a, 72a and 73a and a lower facet 70b,71b, 72b, 73b. In this embodiment the lower facets 70b-73b are ofconstant inclination with respect to the major faces of the panelalthough, of course, the inclination of the lower facet may vary as wellas that of the upper facet.

As can be seen in FIG. 12, light incident at a given angle, for examplearriving from the solar disc, is reflected by the facets 70a-73a througha greater angle near the bottom of the panel than it is near the top ofthe panel with the intention that at the lower part of the panel, wherean observer may look down towards the ground, light from the range ofangles likely to be covered by the solar disc during that part of theday when it is sufficiently bright to cause uncomfortable glare, isstrongly reflected so that the reflected rays lie close to the panel. Inan alternative embodiment the range of variation of inclinations may bereversed so that the light incident at a higher point in the panel isreflected more strongly than light incident at a lower point. Theintention here is to cause divergence of the reflected light so thatthere is no concentration at a given angle which could cause discomfortor dazzling. As can be seen in FIG. 12, the intersection of differentbeams occurs at a distance from the glazing panel equivalent to no morethan twice the thickness of the panel (which may typically be in therange of only a few millimetres) so that an observer cannot position hiseye at any point where reflected rays intersect.

In the embodiment of FIG. 13 the upper or reflective facet of the grooveis convex towards the direction of incident light, causing divergence inthe reflected beam as illustrated, and likewise, in FIG. 16 the upperfacet is concave towards the direction of incident light (which althoughit involves intersection of reflected beams, nevertheless producesdivergence of the reflected light at any practical viewing distance.

As far as manufacturing techniques are concerned, it may be difficult toproduce the embodiment of FIG. 13, in which the reflector facet isconvex, but this may be overcome using suitable techniques.

The other problem which is overcome by the embodiments of FIGS. 12, 13and 14 is that of the possibility of focused hot spots on the ceilingfrom the solar disc. By creating a wide divergence in the light arrivingfrom a given direction, upon reflection the light from the solar disc isspread over a wide area of the ceiling. This also minimises anybrightness variations caused by intensity differences in light arrivingfrom different directions.

The embodiment of FIG. 15 comprises a composite panel generallyindicated 75 comprising two elements 70, 77 which, in this embodiment,are exactly identical to one another. This simplifies manufacture. Theelement 76 comprises a monolithic transparent body having a flat majorface 78 and a regular array of substantially identical grooves separatedby correspondingly shaped ribs 79. Each rib 79 is defined by a firstface 80 substantially orthogonal to the major face 78, and a second face81 inclined at approximately 30° to the orthogonal face 80. The body 77has a flat major face 82 oppositely from which projects an array ofregular triangular ribs 83 defined by a first, orthogonal face 84 and asecond, inclined face 85 the angle of inclination of which is identicalto that of the inclined face 81 of the triangular rib 79 of the firstelement 76.

The two elements 76, 77 are reversed and inverted with respect to oneanother such that the ribs 79 of the element 76 penetrate the groovesdefined between the ribs 83 of the element 77. The inclined faces 81 and85 are in contact with one another whilst the orthogonal faces 80, 84are separated by a small air gap 86.

The dimensions may be such that the overall thickness of the component75 is in the region of 1.6 mm whilst the ribs are approximately 0.5 mmwide at their root (and correspondingly the tips of the ribs are 0.5 mmapart) and in the region of 1 mm in height.

In order to define the physical configuration of the surfaces definingthe ribs it is possible to identify two ratios, namely the "aspect"ratio namely the ratio between the height t and the peak-to-peakseparation p of the ribs (aspect ratio: t/p) and an asymmetry ratiodefined by the apex location of each rib in relation to its root widthgiven by h/p where h is the distance from one side of the root of a ribto the peak and p is the root width or peak-to-peak separation. In theembodiment of FIG. 1 the dimension h is 0 therefore making the apexlocation ratio h/p=0 whilst the aspect ratio t/p is approximately 2.

The path of several incident rays has been traced assuming that therefractive index of the material from which the elements is made is1.492 whilst the refractive index of the medium between the inclinedfaces 81, 85 (which may be an adhesive) is 1.38 and the medium betweenthe orthogonal faces 80, 84 is air of refractive index 1.00. Thisembodiment has a particularly valuable feature in that incident lightapproximately 5° above the horizontal is reflected by multiple internalreflections; light incident horizontally is transmitted substantiallyundeviated; and light above a certain critical angle is transmittedthrough the component after a single reflection at the interface betweenthe ribs 79 and the air gap 86 defined by the orthogonal faces 80. Theretro-reflection of the rays illustrated provides a sunshading effectwhich prevents the transmission into the building of direct rays fromthe solar disk at a selected range of elevations to avoid glare.Suitable choice of the aspect ratio t/p, peak offset position h/p andthe refractive index of the material, as well as the thickness of thematerial can vary the inclination at which this sun shading effectoccurs. In this respect the thickness of that part of the elementbetween the bottoms of the grooves and the flat major face is ofsignificance in determining this aspect of the behaviour of the opticalcomponent of the invention.

Although embodiments of the present invention may be used, as shown inFIG. 15, in a purely vertical orientation, they may be adapted foradjustable inclination about a horizontal axis, perhaps being formed assupplementary external components on the exterior of a conventionallyglazed window. Or alternatively a window provided with the opticalcomponent of the invention as a part thereof may be mounted so as to betiltable whereby to adjust the angle at which the sun shading effecttakes place. Inclination of the optical component of the presentinvention also greatly increases the amount of light collected fortransmission by including the light very close to the vertical which canbe transmitted into the interior of the building after one or morereflections at internal interfaces. Such close-to-vertical incidentlight is lost to conventional vertical glazing panels. Increases in theoverall internal illumination within a building may thus be achieved.

In the embodiment of FIG. 16 there are two similar optical elements 87,88 having respective major planar faces 89, 90 and an array ofoppositely directed ribs 91, 92 respectively. In this case, however, theribs 91 are defined by a flat planar face 93 on one side whilst beingdefined by two, slightly inclined planar faces 94, 95 on the other. Theeffect of this, in relation to the embodiment of FIG. 1, is to define anairspace 96 between adjacent ribs 91, 92 which is trapezoidal in shape.This serves to direct the bundles of light rays into a narrowertransverse dimension after transmission across the air gap 96, as shownby the two examplary boundary rays 97, 98. This allows less scope forthe edges of a bundle of rays to behave differently upon reflection atthe inner major face 90 of the element 88. The embodiment of FIG. 3 isillustrated at an inclination to demonstrate the awning effect referredto in relation to the embodiment of FIG. 15.

The embodiment of FIG. 17 is, again, an optical component 99 comprisingtwo identical elements 100, 101 having flat planar faces 102, 103 andoppositely directed symmetrical ribs 104, 105. Not only are the ribs104, 105 symmetrical and identical in shape, but also the groovesdefined between adjacent ribs 104, 105 are of exactly the same shape sothat when the two elements 100, 101 are fitted together as shown in FIG.17 the two sets of grooves are entirely filled by the correspondinglyshaped sets of ribs 104, 105. Again the contacting faces of the ribs104, 105 may be bonded by an adhesive having a selected refractive indexthereby influencing the optical behaviour of the component. In solidoutline are shown the ray traces of two rays 106, 107 incidentperpendicular to the external face 102 of the outer element 100. If therefractive index of the medium between the two elements is air (ofassumed refractive index 1.00) the rays follow the paths indicated insolid outline to be reflected back on themselves whereas if therefractive index between the two elements 100, 101 is determined by anadhesive at, say, 1.40 then the incident rays 106, 107 would betransmitted along the broken outline paths shown rather than beingreflected. These design options allow the designer to determine theoptical properties of the component in dependence on the requiredfunction.

Turning now to FIG. 18 an embodiment similar to that of FIG. 17 (in thatthe oppositely directed ribs are identical) is shown, but in this casethe ribs (in this embodiment identified by the reference numerals 108,109) are slightly asymmetric with respective surface angles at 94.9° and67.5°. The aspect ratio t/p is 2. If the refractive index of the mediumbetween the elements 110, 111 is 1.00 then an incident ray illustratedas 112 will be reflected at the interface between two adjacent ribs 108,109 to be transmitted at an increased elevation within the interior ofthe building. The incident ray 112 illustrated is chosen to be thatwhich, upon refraction at the incident face 113 of the element 110 istransmitted through the element 110 parallel to the more inclinedinterface between adjacent ribs 108, 109 and, by comparison with FIG. 19the reversibility of the transmission path can be seen. In FIG. 19 thereis shown a component 115 comprising two elements 116, 117 havingrespective ribs 118, 119 a first face 120 of which inclined at the sameangle as the corresponding interface 121 in the embodiment of FIG. 18,but the more inclined interface 122 is oppositely directed from that ofthe corresponding inclined interface 123 in the embodiment of FIG. 18.Notwithstanding this the path of the ray 112 can be seen to besubstantially the same since at its transmission through the interface122 it is not deviated if the refractive index of the medium between theribs is 1.00, and therefore only the total internal reflection at theinterface 120 occurs, which is exactly the same as in the embodiment ofFIG. 18.

FIG. 20 illustrates another embodiment in which the peak offset ratioh/p is 0 or 1, which may be used for imaging purposes where, as can beseen, a family of rays 130 incident on one face 131 of an element 132are reflected at orthogonal interfaces 133 to be transmitted throughinclined interfaces 134 and refracted again at a plane major face 135 ofthe second element 136 which is identical in form to the element 132.

In the embodiment of FIG. 21 is shown another arrangement in which thecomponent 137 comprises two elements 138, 139 which have plane majorfaces 140, 141 and symmetrical ribs 142, 143 separated by symmetricaland correspondingly shaped grooves, (not referenced) in a form such thatthe ribs 142, 143 interpenetrate one another and both symmetricallyinclined faces are in contact to define interfaces 144, 145. The aspectratio in this embodiment is approximately 1.9 and the peak offset ratiois 1/2 (thereby defining a symmetrical configuration. For certainincident angles typified by the incident ray 146 the component acts as aplane reflector by multiple internal reflections, with a virtualreflection plane identified by the chain line 147. This reflectionoccurs only over a limited range of incident angles, however, and lightis transmitted through the component 137 at angles of incidence outsidethis range. Such an embodiment may be useful for a part-time reflectorwhere reflection or transmission can be achieved by varying theinclination of the component with respect to the observer, or by movingthe observer's head with respect to a fixed component. Such a reflectormay have value, for example, as a rear view mirror of extended width,suitable for a truck or for towing a caravan, where forward vision andrear view are both required from the same part of the field of view, andboth can be achieved at will by the observer.

FIG. 22 illustrates another embodiment of the invention in whichinterpenetrating ribs of different but corresponding shape, identifiedby the reference numerals 150, 151 define a family of interfaces 160parallel to one another and inclined to the major faces 148, 149 ofrespective optical components 152, 153. In this embodiment, as can beseen from FIG. 22, illumination at the same angle of incidence may betransmitted differently in dependence on its transverse position. Herethe incident ray 154 strikes a first facet of the interface 155 to betransmitted approximately orthogonally of the major face 149 whereas anidentically inclined incident ray 156 strikes a second facet of theinterface 155 and is reflected at a sharper angle, and consequentlyrefracted more steeply at the exit face 149. In this embodiment thethickness of material between the face 148 and the roots of the ribs 151is greater.

It is not essential for the ribs to penetrate the grooves and in theembodiment of FIG. 23 there is shown a component 160 comprising twoidentical elements 161, 162 having sets of inclined V-shaped grooves163, 164 spaced from one another by a greater distance than the width ofthe groove. In this case the grooves may be typically of the order of 1mm at their widest point, whilst the separation between adjacent groovesmay be of the order of 2 or 3 mm. The facing surfaces of the elements161, 162 are bonded by an adhesive 165 which preferably has the samerefractive index as the material of the elements 161, 162 so that thecomposite element 160 effectively behaves as a monolithic body withtrapezoidal voids defined by pairs of grooves 163, 164. Such a structureis typically suitable to be made in glass.

Another embodiment, similar to that of FIG. 23, but having a differentratio of dimensions is illustrated in FIG. 24. Here the component 170comprises two elements 171, 172 which are identical to one another andhave respective V-section grooves 173, 174 in register with one another,the two elements 171, 172 being bonded by adhesive either betweenadjacent grooves as illustrated by the bonding element 175 or spanningthe grooves as illustrated by the bonding element 176.

In FIG. 25 the form of the elements 181, 182 is similar to that of theelements 171, 172 but the grooves 183, 184 are asymmetrical to provideimproved daylighting performance.

A further embodiment illustrated in FIG. 26 shows how the grooves 193,194 may be formed by pressing in metal or other formers 195 into theotherwise flat faces 196, 197 of planar sheets 198, 199 of glass.Because the formers 195 do not bond intimately with the surfaces of theglass, leaving a small air gap so that total internal reflection cantake place, the formers 195 are effectively "invisible" since incidentlight which would otherwise be blocked by the opacity of the formers isreflected at the interface whereas light incident at a narrow range ofangles about a direction orthogonal to the general plane of thecomponent is transmitted through the component substantially unmodified.

Although in all of the embodiments illustrated the ribs and grooves ofthe elements are directed inwardly towards one another, and this is thepreferred arrangement, it is nevertheless possible for embodiments to beformed in which the ribs and grooves of the two elements to face in thesame direction as one another, for example inwardly of a building, orfor the ribs and grooves to face away from one another.

I claim:
 1. An optical component comprising two substantially planarelements each having a respective plurality of elementary surfaces whichreflect by total internal reflection light incident thereon through thecorresponding said element within a first range of incident anglesassociated with each said elementary surface, and which refract lightincident thereon through the corresponding said element within a secondrange of incident angles associated with each said elementary surface,the configuration of the said elements being such that when the lightfrom a range of directions is incident on the optical component aportion thereof is diverted by total internal reflection at theinterfaces defined by the said elementary surfaces, and at least aportion thereof passes through said elements substantially undeviatedwherein a substantially undistorted view through the optical componentis obtained over at least a limited range of viewing angles.
 2. Theoptical component of claim 1, wherein at least one said substantiallyplanar element has first and second opposite major faces, a plurality ofregular surface formations on said second major face defining saidplurality of elementary surfaces, the said surface formations acting todivert light passing through the component by refraction and reflectioninto at least two different directions.
 3. The optical component ofclaim 2 wherein the said elementary surfaces are substantially planar.4. The optical component of claim 3, wherein some of the said elementarysurfaces lie substantially orthogonal to the said first major face ofthe element, on which light is incident in use.
 5. The optical componentof claim 2, wherein the said elementary surfaces comprise a plurality ofparallel grooves one of the faces of which defines an interface at whichreflection occurs over the said predetermined range of angles ofincident light.
 6. The optical component of claim 5, wherein each saidelementary surface is unsilvered and inclined to the said first majorface of the component on which, in use, light is incident, at an anglesuch that total internal reflection occurs at the interface for lightincident on the said first major face of the component within apredetermined range of angles.
 7. The optical component of claim 5,wherein each said elementary surface is unsilvered and inclined to thesaid first major face of the component on which, in use, light isincident, at an angle such that total internal reflection occurs at theinterface for light incident on the said first major face of thecomponent within a predetermined range of angles.
 8. The opticalcomponent of claim 2, wherein the said first and second opposite majorfaces each have at least a portion of their respective surface areassubstantially parallel to one another.
 9. The optical component of claim2, wherein ore of said first and second opposite major faces is asubstantially flat uninterrupted planar surface.
 10. The opticalcomponent of claim 9, wherein there are further provided means fordiverting a proportion of light incident on the said one major face insuch a way that it travels away from the component on the same sidethereof as the said one major face.
 11. The optical component of claim2, wherein facing major surfaces of the said two optical elements are incontact with one another.
 12. The optical component of claim 11, whereinthere are provided means for varying the physical configuration of thesaid surface formations of at least one said optical element, whereby tovary at least one of the directions and the proportion of refracted andreflected exit light.
 13. The optical component of claim 11, wherein thesaid elementary surfaces of the optical elements interpenetrate oneanother.
 14. The optical component of claim 2, wherein the surfaceformations thereof are directed towards one another and the surfaceformations of one optical element are off-set, parallel to the plane ofthe optical component, with respect to the surface formations of theother said optical element.
 15. The optical component of claim 2,wherein both said substantially planar elements have surface formationsdirected towards one another and the surface formations of one opticalelement are in register, parallel to the plane of the optical component,with the surface formations of the other said optical element.
 16. Theoptical component of claim 1, wherein the elementary surfaces areinclined at different angles at different parts of the said elements,such that, for a given angle of incidence, the angle of reflection isdifferent at different points of incidence over the surface of thecomponent.
 17. The optical component of claim 3, wherein the inclinationof the said elementary surfaces is greater nearer a lower edge of thesaid planar element in relation to a normal upright orientation of use,such that for a given angle of incidence, the angle of reflection isgreater at points of incidence closer to the said lower edge of thecomponent than at points of incidence further from the said lower edge.18. The optical component of claim 1, wherein at least some of the saidelementary surfaces are curved transverse their length.
 19. The opticalcomponent of claim 18, wherein the curvatures of the said at least someof the said elementary surfaces are convex.
 20. The optical component ofclaim 18, wherein the curvatures of the said at least some of the saidelementary surfaces are concave.
 21. The optical component of claim 1,wherein the said two optical elements are located between andrespectively contacted by two rigid, substantially planar, transparentpanels.
 22. The optical component of claim 1, wherein there are furtherprovided means for introducing a fluid of different refractive indexfrom that of air into the interspace between the said two opticalelements whereby to vary at least one of the direction and theproportion of refracted and reflected exit light.
 23. The opticalcomponent of claim 1, wherein for light incident thereon at an anglewithin a predetermined range of incident angles, all of the lighttransmitted through the component travels in substantially the samedirections as the incident light.
 24. An optical component comprising:afirst optically transparent body having two major faces a first of whichis substantially uninterrupted and a second of which is interrupted by aplurality of cavities defined by first and second elementary surfaces, asecond optically transparent body having two major faces a first ofwhich is substantially uninterrupted and a second of which isinterrupted by a plurality of cavities defined by first and secondelementary surfaces, the said first and second optically transparentbodies being juxtaposed with their respective said second major facesfacing one another and the first elementary surfaces of the cavities inthe second major face of the first optically transparent body contactingthe corresponding first elementary surfaces of the cavities in thesecond major face of the second optically transparent body wherein thesaid contacting first elementary surfaces of the cavities in the secondmajor faces of both the first and second optically transparent bodiesallow light incident thereon through the respective said opticallytransparent body at an angle of incidence with the said first elementarysurfaces below a threshold angle to be transmitted therethrough toprovide a view through the optical component and the second elementarysurfaces art to reflect by total internal reflection light incidentthereon through the associated said optically transparent body at anangle of incidence with the said second elementary surfaces above athreshold angle wherein to divert said light out of its incidentdirection, wherein said incident light passes substantially undeviatedthrough said first and second optically transparent bodies.
 25. Theoptical component of claim 24, wherein the elementary surfaces areinclined at different angles at different parts of the said opticallytransparent bodies such that, for a given angle of incidence, the angleof reflection is different at different points of incidence over thesurface of the component.
 26. The optical component of claim 24, whereinthe inclination of the said elementary surfaces is greater nearer thelower edge of the said optically transparent body in relation to anormal upright orientation of use such that for a given angle ofincidence, the angle of reflection is greater at points of incidencecloser to the said lower edge of the body than at points of incidencefurther from the said lower edge.
 27. The optical component of claim 24,wherein the said elementary surfaces are substantially planar.
 28. Theoptical component of claim 24, wherein some of the said secondelementary surfaces lie substantially orthogonal to the said first majorface of the element, on which light is incident in use.
 29. The opticalcomponent of claim 24, wherein at least some of the said elementarysurfaces are curved transverse their length.
 30. The optical componentof claim 29, wherein the curvatures of the said at least some of thesaid elementary surfaces are convex.
 31. The optical component of claim29, wherein the curvatures of the said at least some of the saidelementary surfaces are concave.
 32. The optical component of claim 24,wherein the said cavities comprise a plurality of parallel groovesdefined by respective pairs of first and second elementary surfacesinclined with respect to one another.
 33. The optical component of claim24, wherein each said elementary surface is unsilvered and inclined tothe said first major face of the component on which, in use, light isincident, at an angle such that total internal reflection occurs at theinterface for light incident on the said first major face of thecomponent within a predetermined range of angles.
 34. The opticalcomponent of claim 24, wherein the said first and second opposite majorfaces each have at least a portion of their respective surface areassubstantially parallel to one another.
 35. The optical component ofclaim 24, wherein there are further provided means for diverting aproportion of light incident on the said one major face in such a waythat it travels away from the component on the same side thereof as thesaid one major face.
 36. The optical component of claim 24, wherein thesaid two optical elements are located between and respectively contactedby two rigid, substantially planar, transparent panels.
 37. The opticalcomponent of claim 24, wherein there are further provided means forintroducing a fluid of different refractive index from that of air intothe interspace between the said two optical elements whereby to vary thedirection of refracted and or reflected exit light and/or the proportionof exit light traveling in each of the said two directions.
 38. Theoptical component of claim 24, wherein there are provided means forvarying the physical configuration of the said surface formations of theor each said optical element, whereby to vary the proportion of exitlight traveling in each said direction.
 39. The optical component ofclaim 24, wherein for light incident thereon at an angle within apredetermined range of incident angles, all of the light transmittedthrough the component travels in substantially the same directions asthe incident light.
 40. The optical component of claim 24, wherein theelementary surfaces of one optical element are off-set, parallel to theplane of the optical component, with respect to the elementary surfacesof the other said optical element.
 41. The optical component of claim24, wherein the elementary surfaces of one optical element are inregister, parallel to the plane of the optical component, with theelementary surfaces of the other said optical element.
 42. An opticalcomponent of claim 24, wherein the dimensions of and separation betweenthe elementary surfaces are not substantially larger than about thepupil of the human eye (1 mm) and not smaller than that at whichdiffraction effects predominate (about several micrometers).